Electric arc furnace and crane structure



July 7, 1931. A. E. GREENE 1,313,397

ELECTRIC ARC FURNACE AND CRANE STRUCTURE Filed June, 18, 1930 INVENTORfl/fierf E 'ree/re ATTORNEYS Patented July 7, 1931 UNITED STATES PATENTOFFICE ALBERT n GREENE, or

ELECTRIC ARC FURNACE Application filed June 18,

This invention relates to electric arc furnaces and especially to theelectrode-carrying mechanism or crane structure of such furnaces. Moreparticularly the invention aims to providea mast of improvedconstruction forming a part of the crane structure, and an improved,means for mounting the masts upon the furnace. 7

Electric furnaces of the so-called arc type 10 comprise generally aheating chamber into which a charge of metal scrap or ore is introducedand a plurality of electrodes connected with a source of electricalenergy. By

establishing arcs across the space separating 1 the electrodes from thecharge a circuit is completed through the charge which melts inconsequence "of the terrific heat generated.

The furnace is customarily arranged for tipping movement to pour off themolten metal and the slag. In such type of furnace it is usual to mountthe electrodes for vertical movement to permit maintaining the mosteffective arcing interval between the electrodes and the charge withinthe heating chamber, which interval must necessarily vary in accordancewith changes in the temperature of the charge, the current maintained,and also to compensate for the gradual consumption of the electrodes attheir points during operation of the furnace. For this purpose a craneis usually provided for each electrode which consists essentially of anelectrode holder mounted upon a carriage which is adapted to be raisedand lowered along a mast or standard extending vertically above thefurnace. One object of the present invention is to provide an improvedmounting for the electrode mast by which the weight of the mast iscarried entirely by the base of the furnace. Another object of theinvention is to provide a mast assembly permitting a plurality of maststo be removably attached to the furnace as a unit.

This object is accomplished by providing a combination of several mastsrigidly mounted together to form a mast structure which may be removedbodily for shipment and'which may be attached to the furnace in such amanner as to rest on a suitable supporting member of the furnace proper.

MEDINA, WASHINGTON AND CRANE STRUCTURE 1930. Serial No. 461,947.

This combination mast structure comprises one or more structuralmembers, such as steel plates, at its lower end to which the masts areindividually welded, and another memher at or near the top of the masts,whereby the masts and structural members form a rigidly connected framewhich can be bolted or otherwise attached to the supports on the furnaceshell.

Various types of masts have been used in the past, one of which isdisclosed in Patent No. 1,751,913, of Albert E. Greene, issued March 25,1930, consisting of a structural I- beam, of which the exterior surfacesof the flanges provide tracks for a set of rollers carried by theelectrode carriage. lVhile such type of mast is satisfactory in thosecases where there is little or no tendency to twisting of the mast, aswhere the mast is so mounted upon the tiltable furnace as to be 7 swungin a plane parallel to its web, under conditions where the mast isrigidly affixed to and at one side of the furnace and arranged to swingwith the furnace during its pouring operation in a directiontransversely of the plane of the web there results tortional stressesupon the mast which tend, if not to fracture, at least to causetemporary or per manent deformation of the flanges permitting theelectrode to shift laterally. An important object of the presentinvention is to provide a mast of such rigidity of construction as towithstand these tortional stresses. More particularly this end isattained by providing a mast of such cross-section as to insure thegreatest strength at the points most susceptible to fracture ordeformation.

The above features and others will now be described with reference tothe annexed drawings, in which:

Fig, 1 is a front elevation of an electric arc furnace mounted fortipping movement, showing the manner by which the mast structure andelectrode-carrying mechanism, are connected therewith as contemplated bythe present invention.

Fig. 2 is a plan view of the furnace shown in Fig. 1, the hoists beingomitted;

Fig. 3 is a sectional view of one improved 1 form of mast composed oftwo channel irons.

Fig. 4 is a sectional view of a modified form of mast made up of fourmetal plates rigidly connected together.

Fig. 5 is a sectional view of still another form of mast utilizing anI-beam.

In Fig. 1 of the drawing is shown an arc furnace of a conventional typehaving an upright, generally cylindrical shell 1 forming the meltingchamber into which the scrap material or ore is charged, the furnacebeing mounted upon a pair of rockers 2 to permit tilting in onedirection to discharge its molten contents through the pouring opening 4and tilting in the opposite direction to allow skimming or pouring offthe slag through the charging door 5. For rocking the furnace about itsaxis (0-11. there is provided a piston 6 pivotally connected at one endto the furnace at one side of its axis and having its other endconnected to a plunger working centers and axes.

within a hydraulic cylinder 7. A plurality of electrodes 8, in this casenumbering three, are supported in a normally vertical position above thefurnace shell 1 and extend through its top into the heating chamberwhere the charge of metal scrap is contained. The upper end of eachelectrode is connected to a source of electric current in a manner wellknown in the art.

The electrodes 8 are each arranged for vertical movement by means of acrane consisting generally of an electrode carrying arm 17 mounted upona carriage 22, a vertically extending mast 9 along which the carriage isadapted to travel, and a drum 18 for raising and lowering the carriage.The cranes are constructed as follows: At one side of the cylindricalfurnace shell 1 and aligned at right angles to the transverse axis a-aof the furnace are a series of vertically extending electrode masts 9their lower ends being welded to a lower plate 10 which in turn isremovably bolted upon a platform 10' carried by brackets 11 rigidlyfastened to and supported by the furnace base and rockers 2. These mastsare maintained rigid and in parallelism with each other by means of achannel iron 12 to which the masts are welded and which acts to tietogether their upper ends, and also by means of an intermediate late 13also bolted to a flange 1' extending aterally from the furnace at itstop. In the intermediate plate 13 holes are preferably cut to receivethe masts, the plate and masts then being welded. These holes are cut atthe proper position and angle so that the axes of the electrode armspass approximately through the desired The mast head plate or channelmember 12, as shown in the drawing, may also have holes formed in itcorresponding to those in the intermediate plate 13, the masts beingwelded to this plate.

It will be seen that by this construction the positions of the electrodethree members to which the masts are welded, namely the bottom plate 10,the intermediate plate 13, and the top member 12 unite the masts as aunitary structure which possesses sufficient rigidity to withstand thestresses resulting from tipping the furnace, and which is also capableof being quickly bolted thereto. The weight of the mast structure beingsupported chiefly on the rockers 2 which are mounted below the shell,the shell in consequence is relieved of the weight of this structure,which avoids the occurrence of dangerous stresses which might rupturethe shell when weakened by the high temperatures developed during theoperation of the furnace.

Arranged to travel longitudinally upon each mast Is an arm 17 extendinghor1zontally to a position over the furnace and supporting one of theelectrodes 8. This arm is mounted upon the travelling carriage 22 havinga plurality of rollers 14 positioned to engage opposite flat faces ofthe mast 9 which in customary practice heretofore has consisted ofeither a structural I-beam or a cylindrical post provided with afeather. The rollers 14 are rotatably mounted upon shafts 15 extendingbetween spaced side plates 16 forming a part of a clamp for gripping theelectrode supporting arm 17, the arrangement being such that the mast issurrounded on its four sides by the rollers 14 and the two side plates16. The carriage is arranged to be raised and lowered longitudinally ofthe mast by means of a drum hoist 18 driven by a worm gear forwinding-up and playing out a cable 19 which is trained over a mast headsheave 20, suitably journaled within bearings 21 carried upon channeliron 12, and fastened at its end to the arm 17. The drum hoist issupported upon a plate carried by brackets 18' removably attached to themasts 9 and extending in a direction away from the shell 1. The sheave20 is preferably of large diameter to permit the cable to move withoutinterference from the mast frame but it is understood that the sheavecenter may be so positioned as to permit one cable to pass down throughthe mast if desired. The approximate alignment of the backs of the masts9 allows the gear mounting brackets 18 to be removably attached to therear of the masts away from the shell 1. This affords a very simplemounting for the worm-gear drum hoists 18 on top of the plate carried bythese brackets and permits, ifdesired, placing individual motors beneaththe plate-one for each hoist.

By referring to Fig. 2 it will be apparent that as the furnace is tippedon its rockers 2 there will be a tendency for the electrode carrying arm17 to swing under gravitational influence in the direction indicated bythe arrow in Fig. 2 into a plane perpendicular to the axis a-a. Thistwisting moment due to the relatively great mass composing theelectrode-carrying. arm-and electrode at the end of the arm and due alsoto the-fact that the mast at the point intermediate its length at whichthe stress is applied is of necessity free from adjacent support,frequently approaches a dangerous limit. Such stress as is transmittedto the mast 9 through the rollers 14, it will be seen, must be resistedin greater part by the marginal portions or corners of the mast.Consequently these portions of the mast must be made especially rigidlyunited, as by welding, along their 'tween the flanges and wel surfacesof contact. This results in a mast of "rectangular cross-sectionproviding track members 31 (which may be smoothed by machining so as toofler negligible frictional resistance to the rollers 14) and connectingwalls 32 which unite with the track members at their two longitudinaledges. Tendency of the arm to shift to one side by reason of flexing ofthe flan es is thus avoided. Furthermore, a mast 0 such a cross-sectionmost effectively resists longitudinal bending and offers a firm supportfor the rollers. This type of mast is extremely simple to make while atthe same time affording a high degree of strength and rigidity forcounteracting the tortional stresses incident to tilting of the furnace.Instead of welding, the two channel irons may be bolted or otherwisefirmly fastened together.

Another form of mast of approximately rectangular cross-section is shownin Fig. 4. In this embodiment of the invention, instead of the union oftwo channel'irons along their edges, the mast is composed of two spacedtrack plates 41 of cold rolled steel forming the surface along which therollers travel, these plates being connected by means of two spacingchannels 42 united as by weldin to the track plates 41 adjacent theiredges. his form of mast has all the advantages possessed by the onepreviousl described and in addition provides a dou le thickness of metalat the edges of the mast. It is not necessary however that the walls 42should be constituted of channel irons but these walls may comprise flatplates united at their edges to the track plates 41.

Still another modificationis shown in Fig. 5, in which an I-beam isstrengthened by reinforcing plates 51 extendin ded adjacent the edges ofthe flanges 52. This construction effectively prevents fracturing orbending of the flanges under load as described above.

transversely be- This arran ent does not permit of any adjustment o la li e position of one mast relative to the others; nor does it permit ofany angular shifting of the arm axis-for the purpose of swinging theelectrode to one side ,or the other of its normal position. But theconstruction of the mast is materially simplified and provision is madefor lateral adj ustment of the electrode by other means onthe electrodearm not forming part of the present invention.

The upper ends of the masts 9 may in certain cases project throughopenings formed in the channel iron 12 and the sheaves 20 may be mountedin the sides of the masts 9 which extend above the channel iron 12.

What I claim is:

1. In an electric arc furnace comprising a shell enclosing a heatingchamber and mounted for tilting movement an electrode extending throu hthe top of the shell into the heating cham er, and an arm arranged tosupport the electrode in an upright position above the shell, means forpermitting vertical movement of the arm, said means consisting of a mastrigidly connected at one side of the shell and a carriage for the armhaving rollers arranged to engage opposite a faces of the mast, saidmast being composed of two spaced track members and two spacing elementseach rigidly connected to the track members adjacent the edges of thetrack members.

2. In an electric arc furnace comprising a shell enclosing a heatingchamber and mounted for tilting movement, an electrode extending throu hthe top of the shell into the heating cham er and an arm arranged tosupport the electrode in an upright position above the shell, means forpermittin vertical movement .of the arm consisting 05 a mast rigidlyconnected at one side of the shell and 'a carriage for the arm havingrollers arranged to engage opposite faces of the mast,

said mast being of approximately box formation;

3. In an electric arc furnace comprising a shell enclosing a heatingchamber and mounted for tilting movement, an electrode extending throu hthe top of the shell into the heating cham r and an arm arranged tosupport the electrode in an upright position a ove the shell, means forpermittin vertical movement of the arm consistin o a mast rigidlyconnected at one side of t e shell and a carriage for the arm havinrollers arranged to. engage opposite faces 0 the mast, said mast I beingcomposed of four plates welded togather to provide a mastof-approximately rectangular cross-section.

4. In an electric arc furnace comprising a shell enclosing a heatingchamber and mounted for tilting movement, an electrode extending throughthe top of the shell into the heating chamber and an arm arranged tosupport the electrode in an upright position above the shell, means forpermitting vertical movement of the arm consisting of a mast rigidlyconnected at one side of the shell and a carriage for the arm havingrollers arran ed-to engage opposite faces 0 the mast, sai mast beingcomposed of two channel irons having their edges extended toward and inabutting relation with each other and welded along their line ofjunction.

5. In combination with an electric arc furnace comprising a furnace baseand a shell, a removable electrode crane structure consisting of abottom plate, a plurality of masts welded thereto, an intermediate plateto which the masts" are welded, a plate joining the masts at their tops,means for supporting the bottom plate on the furnace base and means forattaching the intermediate plate to the shell structure. I

6. In combination with an electric arc fur-' nace comprising a furnacebase and a shell enclosing a heating chamber, a removable electrodecrane structure consisting of a bottom plate, a plurality of mastswelded thereto, an lntermediate plate to which the masts are welded, aplate joining the mast-s at'their tops, means for supporting the bottomplate on the furnace base, and means for attaching the intermediateplate to the shell structure, said masts being arranged with their outerflanges in approximate alignment.

1 7. In combination with an electric arc furnace comprising a furnacebase and a shell enclosing a heating chamber, a removable electrodecrane structureconsisting of a bottom plate, a plurality of masts weldedthereto, an intermediate plate to which the masts are welded, a platejoining the masts at their top, means for supporting the bottom plate onthe furnace base, and means for attaching the intermediate plate to theshell structure said masts extending thru openings in the intermediateplate and being welded thereto. 8. In combination with an electric arcfurnace comprising a base, shell supported by the base and enclosing aheating chamber, an electrode extending through the top of the shellinto the heating chamber, and arms arranged to support a plurality ofelectrodes in an upright positionabove the shell, means for permittingvertical movement of the arms consisting of a plurality of masts rigidlyconnected at one side of the shell, a bottom plate,

- an intermediate plate to which the masts are welded, a plate joiningthe masts at their tops, means for supporting the masts on the furnacebase, means for attaching the intermediate late to the shell structure,and a plurality o hoists mounted in a position between the mastsupporting means and the intermediate plate. w

In testimony whereof I aflix m signature.

ALBERT E. G EENE.

